| Summary: | 碩士 === 國立臺灣科技大學 === 化學工程系 === 101 === In this work, the photocatalytic degradation of gaseous toluene over Mn-modified TiO2 under vacuum-UV illumination in a continuous flow reaction was investigated in detail, including addition amount of Mn salt, mechanism of photocatalytic degradation of toluene, and its application in a high flow rate reactor.
In first part, the Mn-modified ceramic filter was prepared with using the Mn-contaning titania sol. Effects of calcination temperature, addition amount of Mn-ion, and titania concentration on physical properties were analyzed by X-ray difftaction (XRD), Ultraviolet-Visible diffuse-reflectance spetra (UV-Vis DRS), photoluminescence (PL), and X-ray photoelectron spectra (XPS), respectively. The results indicated that the content of 1 mol% Mn can reduce the electron-hole recombination rate, leading to highest conversion of toluene. The calcination temperature in preparation procedure should be kept at 400 oC to obtain the optima particle size, degree of crystallization, and ozone affinity for Mn-modified photocatalyst.
In second part, the reaction parameters of toluene concentration, retention time, and relative humidity were applied for realization of VUV/TiO2 reaction kinetics. The immediate products in gas and on catalyst surface were determined by FT-IR, GC-MS, and ATD GC-MS. No obvious immediate in gas was found except CO2, and benzaldehyde was observed on the catalyst surface. It depicted that the immediate maybe almost adsorbed on the catalyst surface, gradually resulting in the deactivation of catalyst. Over 95% of activity for titania filter can recovered by heating deactivated filters at 350 oC for 4 h. The excellent regeneration property of Mn-modified filter was proven in multiple cycles.
Finally, the VUV/Mn-TiO2 reaction concept was applied in a high flow rate condition (18 L/min). 50% of conversion for low-concentration toluene in this system was achieved with the increase in irradiation volume. The conversion of toluene was decreased to 23% as the flow rate was further increase to 60 L/min. This system can be applied as a reference for the design of highly efficient air purification system.
Keywords: Mn-modified TiO2, vacuum UV, ozone decomposition,
catalyst regeneration, degradation of toluene.
|
|---|
